1. Field of the Invention
The present invention relates to an image forming apparatus, for example, an electrophotography type, an electrostatic recording type image forming apparatus, or the like, and more particularly, to a color image forming apparatus such as a color copying machine, a color printer, or the similar apparatus, wherein a plurality of image forming members are provided to form a plurality of images, each different in color, on respective image storing members, and then these images are transferred, one on another, in turn, on the same recording sheet held and transported by a recording sheet transporting member.
2. Description of the Related Art
In a conventional image forming apparatus for forming images on both sides of a recording sheet, the recording sheet is transported by an image-transfer belt for transferring an image on one side of the recording sheet and then the recording sheet is reversed and re-fed to the image-transfer belt for forming an image on the other side of the recording sheet. In the conventional image forming apparatus, a re-fed recording sheet and a newly fed recording sheet may be fed alternatively onto the image-transfer belt. In such an apparatus, the overlapping of two recording sheets should be avoided. Japanese Unexamined Laid-open Patent Publication No. H7(1995)-306550 is directed to avoiding such an overlapping of two recording sheets.
On the other hand, in an image forming apparatus which includes an endless image-transfer belt having a seam and which transfers an image to a recording sheet held on the image-transfer belt from a photosensitive drum, if image transferring is performed when the recording sheet is located on the seam, a portion of the image may not be transferred on the recording sheet, resulting in a poor image. In order to solve the problem, an image forming apparatus has been proposed by, for example, Japanese Unexamined Laid-open Patent Publication No. H5(1993)-2347. The image forming apparatus is provided with a seam detector for detecting the seam. The image forming apparatus controls a feeding of the recording sheet so that the recording sheet does not overlap the seam based on the detected result of the seam detector and the size of the recording sheet.
However, in both of the above-mentioned conventional image forming apparatuses, since a supplying of a recording sheet is not re-tried even though the recording sheet is failed to supply or the recording sheet is supplied at an inappropriate timing, a recording sheet which is supplied from a recording supply cassette may overlap the re-fed recording sheet or the seam of the belt.